1FFMPEG-UTILS(1)                                                FFMPEG-UTILS(1)
2
3
4

NAME

6       ffmpeg-utils - FFmpeg utilities
7

DESCRIPTION

9       This document describes some generic features and utilities provided by
10       the libavutil library.
11

SYNTAX

13       This section documents the syntax and formats employed by the FFmpeg
14       libraries and tools.
15
16   Quoting and escaping
17       FFmpeg adopts the following quoting and escaping mechanism, unless
18       explicitly specified. The following rules are applied:
19
20       •   ' and \ are special characters (respectively used for quoting and
21           escaping). In addition to them, there might be other special
22           characters depending on the specific syntax where the escaping and
23           quoting are employed.
24
25       •   A special character is escaped by prefixing it with a \.
26
27       •   All characters enclosed between '' are included literally in the
28           parsed string. The quote character ' itself cannot be quoted, so
29           you may need to close the quote and escape it.
30
31       •   Leading and trailing whitespaces, unless escaped or quoted, are
32           removed from the parsed string.
33
34       Note that you may need to add a second level of escaping when using the
35       command line or a script, which depends on the syntax of the adopted
36       shell language.
37
38       The function "av_get_token" defined in libavutil/avstring.h can be used
39       to parse a token quoted or escaped according to the rules defined
40       above.
41
42       The tool tools/ffescape in the FFmpeg source tree can be used to
43       automatically quote or escape a string in a script.
44
45       Examples
46
47       •   Escape the string "Crime d'Amour" containing the "'" special
48           character:
49
50                   Crime d\'Amour
51
52       •   The string above contains a quote, so the "'" needs to be escaped
53           when quoting it:
54
55                   'Crime d'\''Amour'
56
57       •   Include leading or trailing whitespaces using quoting:
58
59                   '  this string starts and ends with whitespaces  '
60
61       •   Escaping and quoting can be mixed together:
62
63                   ' The string '\'string\'' is a string '
64
65       •   To include a literal \ you can use either escaping or quoting:
66
67                   'c:\foo' can be written as c:\\foo
68
69   Date
70       The accepted syntax is:
71
72               [(YYYY-MM-DD|YYYYMMDD)[T|t| ]]((HH:MM:SS[.m...]]])|(HHMMSS[.m...]]]))[Z]
73               now
74
75       If the value is "now" it takes the current time.
76
77       Time is local time unless Z is appended, in which case it is
78       interpreted as UTC.  If the year-month-day part is not specified it
79       takes the current year-month-day.
80
81   Time duration
82       There are two accepted syntaxes for expressing time duration.
83
84               [-][<HH>:]<MM>:<SS>[.<m>...]
85
86       HH expresses the number of hours, MM the number of minutes for a
87       maximum of 2 digits, and SS the number of seconds for a maximum of 2
88       digits. The m at the end expresses decimal value for SS.
89
90       or
91
92               [-]<S>+[.<m>...][s|ms|us]
93
94       S expresses the number of seconds, with the optional decimal part m.
95       The optional literal suffixes s, ms or us indicate to interpret the
96       value as seconds, milliseconds or microseconds, respectively.
97
98       In both expressions, the optional - indicates negative duration.
99
100       Examples
101
102       The following examples are all valid time duration:
103
104       55  55 seconds
105
106       0.2 0.2 seconds
107
108       200ms
109           200 milliseconds, that's 0.2s
110
111       200000us
112           200000 microseconds, that's 0.2s
113
114       12:03:45
115           12 hours, 03 minutes and 45 seconds
116
117       23.189
118           23.189 seconds
119
120   Video size
121       Specify the size of the sourced video, it may be a string of the form
122       widthxheight, or the name of a size abbreviation.
123
124       The following abbreviations are recognized:
125
126       ntsc
127           720x480
128
129       pal 720x576
130
131       qntsc
132           352x240
133
134       qpal
135           352x288
136
137       sntsc
138           640x480
139
140       spal
141           768x576
142
143       film
144           352x240
145
146       ntsc-film
147           352x240
148
149       sqcif
150           128x96
151
152       qcif
153           176x144
154
155       cif 352x288
156
157       4cif
158           704x576
159
160       16cif
161           1408x1152
162
163       qqvga
164           160x120
165
166       qvga
167           320x240
168
169       vga 640x480
170
171       svga
172           800x600
173
174       xga 1024x768
175
176       uxga
177           1600x1200
178
179       qxga
180           2048x1536
181
182       sxga
183           1280x1024
184
185       qsxga
186           2560x2048
187
188       hsxga
189           5120x4096
190
191       wvga
192           852x480
193
194       wxga
195           1366x768
196
197       wsxga
198           1600x1024
199
200       wuxga
201           1920x1200
202
203       woxga
204           2560x1600
205
206       wqsxga
207           3200x2048
208
209       wquxga
210           3840x2400
211
212       whsxga
213           6400x4096
214
215       whuxga
216           7680x4800
217
218       cga 320x200
219
220       ega 640x350
221
222       hd480
223           852x480
224
225       hd720
226           1280x720
227
228       hd1080
229           1920x1080
230
231       2k  2048x1080
232
233       2kflat
234           1998x1080
235
236       2kscope
237           2048x858
238
239       4k  4096x2160
240
241       4kflat
242           3996x2160
243
244       4kscope
245           4096x1716
246
247       nhd 640x360
248
249       hqvga
250           240x160
251
252       wqvga
253           400x240
254
255       fwqvga
256           432x240
257
258       hvga
259           480x320
260
261       qhd 960x540
262
263       2kdci
264           2048x1080
265
266       4kdci
267           4096x2160
268
269       uhd2160
270           3840x2160
271
272       uhd4320
273           7680x4320
274
275   Video rate
276       Specify the frame rate of a video, expressed as the number of frames
277       generated per second. It has to be a string in the format
278       frame_rate_num/frame_rate_den, an integer number, a float number or a
279       valid video frame rate abbreviation.
280
281       The following abbreviations are recognized:
282
283       ntsc
284           30000/1001
285
286       pal 25/1
287
288       qntsc
289           30000/1001
290
291       qpal
292           25/1
293
294       sntsc
295           30000/1001
296
297       spal
298           25/1
299
300       film
301           24/1
302
303       ntsc-film
304           24000/1001
305
306   Ratio
307       A ratio can be expressed as an expression, or in the form
308       numerator:denominator.
309
310       Note that a ratio with infinite (1/0) or negative value is considered
311       valid, so you should check on the returned value if you want to exclude
312       those values.
313
314       The undefined value can be expressed using the "0:0" string.
315
316   Color
317       It can be the name of a color as defined below (case insensitive match)
318       or a "[0x|#]RRGGBB[AA]" sequence, possibly followed by @ and a string
319       representing the alpha component.
320
321       The alpha component may be a string composed by "0x" followed by an
322       hexadecimal number or a decimal number between 0.0 and 1.0, which
323       represents the opacity value (0x00 or 0.0 means completely transparent,
324       0xff or 1.0 completely opaque). If the alpha component is not specified
325       then 0xff is assumed.
326
327       The string random will result in a random color.
328
329       The following names of colors are recognized:
330
331       AliceBlue
332           0xF0F8FF
333
334       AntiqueWhite
335           0xFAEBD7
336
337       Aqua
338           0x00FFFF
339
340       Aquamarine
341           0x7FFFD4
342
343       Azure
344           0xF0FFFF
345
346       Beige
347           0xF5F5DC
348
349       Bisque
350           0xFFE4C4
351
352       Black
353           0x000000
354
355       BlanchedAlmond
356           0xFFEBCD
357
358       Blue
359           0x0000FF
360
361       BlueViolet
362           0x8A2BE2
363
364       Brown
365           0xA52A2A
366
367       BurlyWood
368           0xDEB887
369
370       CadetBlue
371           0x5F9EA0
372
373       Chartreuse
374           0x7FFF00
375
376       Chocolate
377           0xD2691E
378
379       Coral
380           0xFF7F50
381
382       CornflowerBlue
383           0x6495ED
384
385       Cornsilk
386           0xFFF8DC
387
388       Crimson
389           0xDC143C
390
391       Cyan
392           0x00FFFF
393
394       DarkBlue
395           0x00008B
396
397       DarkCyan
398           0x008B8B
399
400       DarkGoldenRod
401           0xB8860B
402
403       DarkGray
404           0xA9A9A9
405
406       DarkGreen
407           0x006400
408
409       DarkKhaki
410           0xBDB76B
411
412       DarkMagenta
413           0x8B008B
414
415       DarkOliveGreen
416           0x556B2F
417
418       Darkorange
419           0xFF8C00
420
421       DarkOrchid
422           0x9932CC
423
424       DarkRed
425           0x8B0000
426
427       DarkSalmon
428           0xE9967A
429
430       DarkSeaGreen
431           0x8FBC8F
432
433       DarkSlateBlue
434           0x483D8B
435
436       DarkSlateGray
437           0x2F4F4F
438
439       DarkTurquoise
440           0x00CED1
441
442       DarkViolet
443           0x9400D3
444
445       DeepPink
446           0xFF1493
447
448       DeepSkyBlue
449           0x00BFFF
450
451       DimGray
452           0x696969
453
454       DodgerBlue
455           0x1E90FF
456
457       FireBrick
458           0xB22222
459
460       FloralWhite
461           0xFFFAF0
462
463       ForestGreen
464           0x228B22
465
466       Fuchsia
467           0xFF00FF
468
469       Gainsboro
470           0xDCDCDC
471
472       GhostWhite
473           0xF8F8FF
474
475       Gold
476           0xFFD700
477
478       GoldenRod
479           0xDAA520
480
481       Gray
482           0x808080
483
484       Green
485           0x008000
486
487       GreenYellow
488           0xADFF2F
489
490       HoneyDew
491           0xF0FFF0
492
493       HotPink
494           0xFF69B4
495
496       IndianRed
497           0xCD5C5C
498
499       Indigo
500           0x4B0082
501
502       Ivory
503           0xFFFFF0
504
505       Khaki
506           0xF0E68C
507
508       Lavender
509           0xE6E6FA
510
511       LavenderBlush
512           0xFFF0F5
513
514       LawnGreen
515           0x7CFC00
516
517       LemonChiffon
518           0xFFFACD
519
520       LightBlue
521           0xADD8E6
522
523       LightCoral
524           0xF08080
525
526       LightCyan
527           0xE0FFFF
528
529       LightGoldenRodYellow
530           0xFAFAD2
531
532       LightGreen
533           0x90EE90
534
535       LightGrey
536           0xD3D3D3
537
538       LightPink
539           0xFFB6C1
540
541       LightSalmon
542           0xFFA07A
543
544       LightSeaGreen
545           0x20B2AA
546
547       LightSkyBlue
548           0x87CEFA
549
550       LightSlateGray
551           0x778899
552
553       LightSteelBlue
554           0xB0C4DE
555
556       LightYellow
557           0xFFFFE0
558
559       Lime
560           0x00FF00
561
562       LimeGreen
563           0x32CD32
564
565       Linen
566           0xFAF0E6
567
568       Magenta
569           0xFF00FF
570
571       Maroon
572           0x800000
573
574       MediumAquaMarine
575           0x66CDAA
576
577       MediumBlue
578           0x0000CD
579
580       MediumOrchid
581           0xBA55D3
582
583       MediumPurple
584           0x9370D8
585
586       MediumSeaGreen
587           0x3CB371
588
589       MediumSlateBlue
590           0x7B68EE
591
592       MediumSpringGreen
593           0x00FA9A
594
595       MediumTurquoise
596           0x48D1CC
597
598       MediumVioletRed
599           0xC71585
600
601       MidnightBlue
602           0x191970
603
604       MintCream
605           0xF5FFFA
606
607       MistyRose
608           0xFFE4E1
609
610       Moccasin
611           0xFFE4B5
612
613       NavajoWhite
614           0xFFDEAD
615
616       Navy
617           0x000080
618
619       OldLace
620           0xFDF5E6
621
622       Olive
623           0x808000
624
625       OliveDrab
626           0x6B8E23
627
628       Orange
629           0xFFA500
630
631       OrangeRed
632           0xFF4500
633
634       Orchid
635           0xDA70D6
636
637       PaleGoldenRod
638           0xEEE8AA
639
640       PaleGreen
641           0x98FB98
642
643       PaleTurquoise
644           0xAFEEEE
645
646       PaleVioletRed
647           0xD87093
648
649       PapayaWhip
650           0xFFEFD5
651
652       PeachPuff
653           0xFFDAB9
654
655       Peru
656           0xCD853F
657
658       Pink
659           0xFFC0CB
660
661       Plum
662           0xDDA0DD
663
664       PowderBlue
665           0xB0E0E6
666
667       Purple
668           0x800080
669
670       Red 0xFF0000
671
672       RosyBrown
673           0xBC8F8F
674
675       RoyalBlue
676           0x4169E1
677
678       SaddleBrown
679           0x8B4513
680
681       Salmon
682           0xFA8072
683
684       SandyBrown
685           0xF4A460
686
687       SeaGreen
688           0x2E8B57
689
690       SeaShell
691           0xFFF5EE
692
693       Sienna
694           0xA0522D
695
696       Silver
697           0xC0C0C0
698
699       SkyBlue
700           0x87CEEB
701
702       SlateBlue
703           0x6A5ACD
704
705       SlateGray
706           0x708090
707
708       Snow
709           0xFFFAFA
710
711       SpringGreen
712           0x00FF7F
713
714       SteelBlue
715           0x4682B4
716
717       Tan 0xD2B48C
718
719       Teal
720           0x008080
721
722       Thistle
723           0xD8BFD8
724
725       Tomato
726           0xFF6347
727
728       Turquoise
729           0x40E0D0
730
731       Violet
732           0xEE82EE
733
734       Wheat
735           0xF5DEB3
736
737       White
738           0xFFFFFF
739
740       WhiteSmoke
741           0xF5F5F5
742
743       Yellow
744           0xFFFF00
745
746       YellowGreen
747           0x9ACD32
748
749   Channel Layout
750       A channel layout specifies the spatial disposition of the channels in a
751       multi-channel audio stream. To specify a channel layout, FFmpeg makes
752       use of a special syntax.
753
754       Individual channels are identified by an id, as given by the table
755       below:
756
757       FL  front left
758
759       FR  front right
760
761       FC  front center
762
763       LFE low frequency
764
765       BL  back left
766
767       BR  back right
768
769       FLC front left-of-center
770
771       FRC front right-of-center
772
773       BC  back center
774
775       SL  side left
776
777       SR  side right
778
779       TC  top center
780
781       TFL top front left
782
783       TFC top front center
784
785       TFR top front right
786
787       TBL top back left
788
789       TBC top back center
790
791       TBR top back right
792
793       DL  downmix left
794
795       DR  downmix right
796
797       WL  wide left
798
799       WR  wide right
800
801       SDL surround direct left
802
803       SDR surround direct right
804
805       LFE2
806           low frequency 2
807
808       Standard channel layout compositions can be specified by using the
809       following identifiers:
810
811       mono
812           FC
813
814       stereo
815           FL+FR
816
817       2.1 FL+FR+LFE
818
819       3.0 FL+FR+FC
820
821       3.0(back)
822           FL+FR+BC
823
824       4.0 FL+FR+FC+BC
825
826       quad
827           FL+FR+BL+BR
828
829       quad(side)
830           FL+FR+SL+SR
831
832       3.1 FL+FR+FC+LFE
833
834       5.0 FL+FR+FC+BL+BR
835
836       5.0(side)
837           FL+FR+FC+SL+SR
838
839       4.1 FL+FR+FC+LFE+BC
840
841       5.1 FL+FR+FC+LFE+BL+BR
842
843       5.1(side)
844           FL+FR+FC+LFE+SL+SR
845
846       6.0 FL+FR+FC+BC+SL+SR
847
848       6.0(front)
849           FL+FR+FLC+FRC+SL+SR
850
851       hexagonal
852           FL+FR+FC+BL+BR+BC
853
854       6.1 FL+FR+FC+LFE+BC+SL+SR
855
856       6.1 FL+FR+FC+LFE+BL+BR+BC
857
858       6.1(front)
859           FL+FR+LFE+FLC+FRC+SL+SR
860
861       7.0 FL+FR+FC+BL+BR+SL+SR
862
863       7.0(front)
864           FL+FR+FC+FLC+FRC+SL+SR
865
866       7.1 FL+FR+FC+LFE+BL+BR+SL+SR
867
868       7.1(wide)
869           FL+FR+FC+LFE+BL+BR+FLC+FRC
870
871       7.1(wide-side)
872           FL+FR+FC+LFE+FLC+FRC+SL+SR
873
874       7.1(top)
875           FL+FR+FC+LFE+BL+BR+TFL+TFR
876
877       octagonal
878           FL+FR+FC+BL+BR+BC+SL+SR
879
880       cube
881           FL+FR+BL+BR+TFL+TFR+TBL+TBR
882
883       hexadecagonal
884           FL+FR+FC+BL+BR+BC+SL+SR+WL+WR+TBL+TBR+TBC+TFC+TFL+TFR
885
886       downmix
887           DL+DR
888
889       22.2
890           FL+FR+FC+LFE+BL+BR+FLC+FRC+BC+SL+SR+TC+TFL+TFC+TFR+TBL+TBC+TBR+LFE2+TSL+TSR+BFC+BFL+BFR
891
892       A custom channel layout can be specified as a sequence of terms,
893       separated by '+'.  Each term can be:
894
895       •   the name of a single channel (e.g. FL, FR, FC, LFE, etc.), each
896           optionally containing a custom name after a '@', (e.g. FL@Left,
897           FR@Right, FC@Center, LFE@Low_Frequency, etc.)
898
899       A standard channel layout can be specified by the following:
900
901       •   the name of a single channel (e.g. FL, FR, FC, LFE, etc.)
902
903       •   the name of a standard channel layout (e.g. mono, stereo, 4.0,
904           quad, 5.0, etc.)
905
906       •   a number of channels, in decimal, followed by 'c', yielding the
907           default channel layout for that number of channels (see the
908           function "av_channel_layout_default"). Note that not all channel
909           counts have a default layout.
910
911       •   a number of channels, in decimal, followed by 'C', yielding an
912           unknown channel layout with the specified number of channels. Note
913           that not all channel layout specification strings support unknown
914           channel layouts.
915
916       •   a channel layout mask, in hexadecimal starting with "0x" (see the
917           "AV_CH_*" macros in libavutil/channel_layout.h.
918
919       Before libavutil version 53 the trailing character "c" to specify a
920       number of channels was optional, but now it is required, while a
921       channel layout mask can also be specified as a decimal number (if and
922       only if not followed by "c" or "C").
923
924       See also the function "av_channel_layout_from_string" defined in
925       libavutil/channel_layout.h.
926

EXPRESSION EVALUATION

928       When evaluating an arithmetic expression, FFmpeg uses an internal
929       formula evaluator, implemented through the libavutil/eval.h interface.
930
931       An expression may contain unary, binary operators, constants, and
932       functions.
933
934       Two expressions expr1 and expr2 can be combined to form another
935       expression "expr1;expr2".  expr1 and expr2 are evaluated in turn, and
936       the new expression evaluates to the value of expr2.
937
938       The following binary operators are available: "+", "-", "*", "/", "^".
939
940       The following unary operators are available: "+", "-".
941
942       The following functions are available:
943
944       abs(x)
945           Compute absolute value of x.
946
947       acos(x)
948           Compute arccosine of x.
949
950       asin(x)
951           Compute arcsine of x.
952
953       atan(x)
954           Compute arctangent of x.
955
956       atan2(x, y)
957           Compute principal value of the arc tangent of y/x.
958
959       between(x, min, max)
960           Return 1 if x is greater than or equal to min and lesser than or
961           equal to max, 0 otherwise.
962
963       bitand(x, y)
964       bitor(x, y)
965           Compute bitwise and/or operation on x and y.
966
967           The results of the evaluation of x and y are converted to integers
968           before executing the bitwise operation.
969
970           Note that both the conversion to integer and the conversion back to
971           floating point can lose precision. Beware of unexpected results for
972           large numbers (usually 2^53 and larger).
973
974       ceil(expr)
975           Round the value of expression expr upwards to the nearest integer.
976           For example, "ceil(1.5)" is "2.0".
977
978       clip(x, min, max)
979           Return the value of x clipped between min and max.
980
981       cos(x)
982           Compute cosine of x.
983
984       cosh(x)
985           Compute hyperbolic cosine of x.
986
987       eq(x, y)
988           Return 1 if x and y are equivalent, 0 otherwise.
989
990       exp(x)
991           Compute exponential of x (with base "e", the Euler's number).
992
993       floor(expr)
994           Round the value of expression expr downwards to the nearest
995           integer. For example, "floor(-1.5)" is "-2.0".
996
997       gauss(x)
998           Compute Gauss function of x, corresponding to "exp(-x*x/2) /
999           sqrt(2*PI)".
1000
1001       gcd(x, y)
1002           Return the greatest common divisor of x and y. If both x and y are
1003           0 or either or both are less than zero then behavior is undefined.
1004
1005       gt(x, y)
1006           Return 1 if x is greater than y, 0 otherwise.
1007
1008       gte(x, y)
1009           Return 1 if x is greater than or equal to y, 0 otherwise.
1010
1011       hypot(x, y)
1012           This function is similar to the C function with the same name; it
1013           returns "sqrt(x*x + y*y)", the length of the hypotenuse of a right
1014           triangle with sides of length x and y, or the distance of the point
1015           (x, y) from the origin.
1016
1017       if(x, y)
1018           Evaluate x, and if the result is non-zero return the result of the
1019           evaluation of y, return 0 otherwise.
1020
1021       if(x, y, z)
1022           Evaluate x, and if the result is non-zero return the evaluation
1023           result of y, otherwise the evaluation result of z.
1024
1025       ifnot(x, y)
1026           Evaluate x, and if the result is zero return the result of the
1027           evaluation of y, return 0 otherwise.
1028
1029       ifnot(x, y, z)
1030           Evaluate x, and if the result is zero return the evaluation result
1031           of y, otherwise the evaluation result of z.
1032
1033       isinf(x)
1034           Return 1.0 if x is +/-INFINITY, 0.0 otherwise.
1035
1036       isnan(x)
1037           Return 1.0 if x is NAN, 0.0 otherwise.
1038
1039       ld(var)
1040           Load the value of the internal variable with number var, which was
1041           previously stored with st(var, expr).  The function returns the
1042           loaded value.
1043
1044       lerp(x, y, z)
1045           Return linear interpolation between x and y by amount of z.
1046
1047       log(x)
1048           Compute natural logarithm of x.
1049
1050       lt(x, y)
1051           Return 1 if x is lesser than y, 0 otherwise.
1052
1053       lte(x, y)
1054           Return 1 if x is lesser than or equal to y, 0 otherwise.
1055
1056       max(x, y)
1057           Return the maximum between x and y.
1058
1059       min(x, y)
1060           Return the minimum between x and y.
1061
1062       mod(x, y)
1063           Compute the remainder of division of x by y.
1064
1065       not(expr)
1066           Return 1.0 if expr is zero, 0.0 otherwise.
1067
1068       pow(x, y)
1069           Compute the power of x elevated y, it is equivalent to "(x)^(y)".
1070
1071       print(t)
1072       print(t, l)
1073           Print the value of expression t with loglevel l. If l is not
1074           specified then a default log level is used.  Returns the value of
1075           the expression printed.
1076
1077           Prints t with loglevel l
1078
1079       random(x)
1080           Return a pseudo random value between 0.0 and 1.0. x is the index of
1081           the internal variable which will be used to save the seed/state.
1082
1083       root(expr, max)
1084           Find an input value for which the function represented by expr with
1085           argument ld(0) is 0 in the interval 0..max.
1086
1087           The expression in expr must denote a continuous function or the
1088           result is undefined.
1089
1090           ld(0) is used to represent the function input value, which means
1091           that the given expression will be evaluated multiple times with
1092           various input values that the expression can access through ld(0).
1093           When the expression evaluates to 0 then the corresponding input
1094           value will be returned.
1095
1096       round(expr)
1097           Round the value of expression expr to the nearest integer. For
1098           example, "round(1.5)" is "2.0".
1099
1100       sgn(x)
1101           Compute sign of x.
1102
1103       sin(x)
1104           Compute sine of x.
1105
1106       sinh(x)
1107           Compute hyperbolic sine of x.
1108
1109       sqrt(expr)
1110           Compute the square root of expr. This is equivalent to "(expr)^.5".
1111
1112       squish(x)
1113           Compute expression "1/(1 + exp(4*x))".
1114
1115       st(var, expr)
1116           Store the value of the expression expr in an internal variable. var
1117           specifies the number of the variable where to store the value, and
1118           it is a value ranging from 0 to 9. The function returns the value
1119           stored in the internal variable.  Note, Variables are currently not
1120           shared between expressions.
1121
1122       tan(x)
1123           Compute tangent of x.
1124
1125       tanh(x)
1126           Compute hyperbolic tangent of x.
1127
1128       taylor(expr, x)
1129       taylor(expr, x, id)
1130           Evaluate a Taylor series at x, given an expression representing the
1131           ld(id)-th derivative of a function at 0.
1132
1133           When the series does not converge the result is undefined.
1134
1135           ld(id) is used to represent the derivative order in expr, which
1136           means that the given expression will be evaluated multiple times
1137           with various input values that the expression can access through
1138           ld(id). If id is not specified then 0 is assumed.
1139
1140           Note, when you have the derivatives at y instead of 0,
1141           "taylor(expr, x-y)" can be used.
1142
1143       time(0)
1144           Return the current (wallclock) time in seconds.
1145
1146       trunc(expr)
1147           Round the value of expression expr towards zero to the nearest
1148           integer. For example, "trunc(-1.5)" is "-1.0".
1149
1150       while(cond, expr)
1151           Evaluate expression expr while the expression cond is non-zero, and
1152           returns the value of the last expr evaluation, or NAN if cond was
1153           always false.
1154
1155       The following constants are available:
1156
1157       PI  area of the unit disc, approximately 3.14
1158
1159       E   exp(1) (Euler's number), approximately 2.718
1160
1161       PHI golden ratio (1+sqrt(5))/2, approximately 1.618
1162
1163       Assuming that an expression is considered "true" if it has a non-zero
1164       value, note that:
1165
1166       "*" works like AND
1167
1168       "+" works like OR
1169
1170       For example the construct:
1171
1172               if (A AND B) then C
1173
1174       is equivalent to:
1175
1176               if(A*B, C)
1177
1178       In your C code, you can extend the list of unary and binary functions,
1179       and define recognized constants, so that they are available for your
1180       expressions.
1181
1182       The evaluator also recognizes the International System unit prefixes.
1183       If 'i' is appended after the prefix, binary prefixes are used, which
1184       are based on powers of 1024 instead of powers of 1000.  The 'B' postfix
1185       multiplies the value by 8, and can be appended after a unit prefix or
1186       used alone. This allows using for example 'KB', 'MiB', 'G' and 'B' as
1187       number postfix.
1188
1189       The list of available International System prefixes follows, with
1190       indication of the corresponding powers of 10 and of 2.
1191
1192       y   10^-24 / 2^-80
1193
1194       z   10^-21 / 2^-70
1195
1196       a   10^-18 / 2^-60
1197
1198       f   10^-15 / 2^-50
1199
1200       p   10^-12 / 2^-40
1201
1202       n   10^-9 / 2^-30
1203
1204       u   10^-6 / 2^-20
1205
1206       m   10^-3 / 2^-10
1207
1208       c   10^-2
1209
1210       d   10^-1
1211
1212       h   10^2
1213
1214       k   10^3 / 2^10
1215
1216       K   10^3 / 2^10
1217
1218       M   10^6 / 2^20
1219
1220       G   10^9 / 2^30
1221
1222       T   10^12 / 2^40
1223
1224       P   10^15 / 2^50
1225
1226       E   10^18 / 2^60
1227
1228       Z   10^21 / 2^70
1229
1230       Y   10^24 / 2^80
1231

SEE ALSO

1233       ffmpeg(1), ffplay(1), ffprobe(1), libavutil(3)
1234

AUTHORS

1236       The FFmpeg developers.
1237
1238       For details about the authorship, see the Git history of the project
1239       (https://git.ffmpeg.org/ffmpeg), e.g. by typing the command git log in
1240       the FFmpeg source directory, or browsing the online repository at
1241       <https://git.ffmpeg.org/ffmpeg>.
1242
1243       Maintainers for the specific components are listed in the file
1244       MAINTAINERS in the source code tree.
1245
1246
1247
1248                                                               FFMPEG-UTILS(1)